Hydrodesulfurization process



Patented July 21,1953 r UNITED STATES PATENT, OFFICE" t 9 2,646,388 a VA HYDRODESULFURIZATION PROCESS Vincent L. Crawford, Fox Chapel, Pa.,assignor V to Gulf Research & Development Company, Pittsburgh, Pa., acorporation of Delaware No Drawing. Application Aprilzo, 1951,

1 Serial No. 222,150

This invention relates toimprovements in the 'desulfurization ofhydrocarbons rutilizing a I nickel-containing desulfurization contact orcatalytic agent.

Contact and catalytic agents containing free or reduced nickel may beused for desulfurizing petroleum oil either by absorbingsulfur from theoil through the formation of sulfur compounds of nickel, or bycatalyzing the conversion of the sulfur in the oil into hydrogen sulfidewhich is washed from the product.- See for instance Cornell applicationSerial No. 92,436, filed May 10, 1949, now U. S. Patent 2,614,066,McAfee ap-' plication Serial No. 63,157, filed December 2, 1948,

now abandoned, and us. Patents 2,070,295,-

2,298,347, and 2,406,200 which refer to the 'employment of 'metallicnickel as a desulfurization contact or catalyst.

In such usagethe nickel progressively loses desulfurizing activitybecause of contamination by sulfur and/or carbonaceous-'1;

materials. It is therefore necessary periodically to regenerate andreactivate the nickeliferous agent by oxidizing to remove sulfur andcarbonaceous contaminants and by then reducing with hydrogen gas toreconvert a substantial portion of the nickel therein'to the freemetallic state.

This reduction is an exothermic reaction and y the contact is not at theproper temperature for the on-stream phase of the desulfurizationprocess and must be either heated or cooled with resulting expense andtime loss to attain the required temperature for continuation of thedesulfurization process. I

' This invention has 'for an object to provide 'tion ofa nickel saltsuch as nickel nitrate, drya method for desulfurizing hydrocarbonswhere'- in the temperature is controlled during thereactivation of anoxidized 'nickeliferous contact or catalyst.

A further object is to provide a method for desulfurizing hydrocarbonsin which the nickeliferous contact or catalytic agent used in theprocess is reactivated by a controlled reduction whereby damage to theagent due to excessive temperature during reduction is avoided.

A still further object is to provide a process for desulfurizinghydrocarbons inwhich the nickeliferous contact or catalytic agent usedin the process is reactivated by a controlled reduction, whereby thepressure of the system and the temperature of the agent at the end ofthe reduction are substantially equal to the pressure and temperaturerequired for the on-stream 4 Claims. (01. 196- 28) These and otherobjects are accomplished by the following invention in which a sulfurcontaining hydrocarbon in vapor phase is desulfurized by contacting itat elevated pressure and ata temperature between about 820 and 875F.with hydrogen and a nickeliferous agent comprising between about 15 and25 per cent nickel calculated as oxide deposited on a porous support,asubstantial portion of said nickel being in the metallic form,terminating the contact of vapor, hydrogen, and nickeliferou's agentwhen regeneration is required, depressuring, regenerating thenickeliferous agent by combustion, at least partially reducing theregenerated nickeliferous agent by treating said agent at an initialreduction temperature between about Z50 and 800 F. and at a pressureapproximately equal to the reaction-pressure with a mixture of steam andreducing gas, the mol ratio of'stea'r n to re- -ducing gas being betweenabout 4.511 and 28:1 and being such as to give said agent'a finaltemperature after reduction atleast about 40 F.

higher than the initial reduction temperature but between about 820 and875 F., terminating the flow of steam and immediately contacting vaporsof the sulfur containing hydrocarbon with hydrogen and the regeneratedand at least partially-reduced nickeliferous agent while still atapproximately said final. temperature and reaction pressure.

The nickeliferous agent herein referred to includes the sulfur absorbentcontact type which desulfurizes'by combining with sulfur in the oil;

the catalytic type which catalyzes conversion of sulfur in the oil intohydrogen sulfide which may belwashed from the product; and the typewhich initially in the process is sulfur absorbent but becomes catalyticafter being sulfurized in the course of the desulfurization process.These 'n'ickeliferous' agents may be prepared by impregnating aporous's'upport material with a soluing. and calcining to form nickeloxide on the support, and at least partially reducing the oxidized massbytreatment with a reducing gas at elevated'temp'erature. v'lhe'agentssuitable for use in my process contain between about 15 and 25 per centby weight nickel calculated asoxide based on the total weight ofthesupport and agent. form of free metallic nickel, nickel oxide, nickelsulfate, or nickel sulfide but will contain at least a substantialamount of free nickel at the beginning of the desulfurization process.Among the suitable porous support materials are, alumina, kieselguhr,silica gel, aluminum silicates, bauxite, Alfrax; Magnesol, Porocel, orsilicaalumina carriers, especially of the cracking catalyst type whetheractive or inactive for cracking.

My process may be employedto desulfurize.

The agents may contain nickel in the various sulfur-containinghydrocarbons such as gasoline, naphtha, gas oil etc. but is particularlyadapted for desulfurizing sulfur-containing heavy deposited on a poroussupport under the following preferred conditions: temperature betweenabout 820 and 875 F., pressure between about 300 and 1000 p. s. i.;liquid hourly space velocity of the oil, between about 0.2 and 6.0volumes of oil per volume of nickeliferous agent; hydrogen concentrationbetween about 1000 and 10,000 or more cubic feet per barrel of oil.During this processv sulfur is removed from the oil either by combiningwith the nickel in the agent or by forming hydrogen sulfide which isremoved from the product by caustic washing or other suitable method. Ineither case, the nickeliferous agent progressively loses itsdesulfurizing activity during the process because of the formation ofsulfur and/or carbonaceous contaminants on the agent.

When the deposition of the contaminants has seriously lowered thedesulfurizing activity of the nickeliferous agent, the contacting withoil vapors isterminated, the system is depressured and the agent isregenerated by contacting with an oxygen-containing regeneration gas atan elevated temperature to burn off carbonaceous deposits and at leastpartially remove sulfur combined with nickel thus forming nickel oxide.Following the regeneration theagent is reactivated by treatment with areducing gas at approximately the pressure desired in the reaction phaseor onstream' phase to reconvert a substantial portion of the nickel tothe metallic state. This reduction reactivation must be initiated at atemperature between 750 and 800 F. If an initial temperature below about750 F. is used the reduction does not proceed satisfactorily and if atemperature above about 800 F. is used initially it is very difficultand uneconomical to restrict the final temperature to the desiredcn-stream temperature. I therefore control the temperature of thepreceding oxidation treatment so that the nickeliferous agent at the endof the oxidationtreatment will be at the proper temperature forinitiating the reduction reactivation. Such control of the regenerationtemperature may be accomplished by regulating the amount of oxygen inthe regeneration gas and/or the temperature of the diluent gas which isusually steam.

Durin regeneration by oxidation of a body of catalytic or contactmaterial of the type employed in my process, a burning Zone progressesthrough the body of material from one end to the other. Unless steps aretaken to avoid it, in the final stages of the regeneration the firstoxidized portion of the material will have cooled and will be at a lowertemperature than the subsequently oxidized portions. This may be avoidedand a uniform temperature throughout the catalytic or contact materialmay be obtained by preheating the regeneration gas to a suitabletemperature (e. g. between about 750 and- 800 F.) to give the desiredinitial temperature for reduction throughout the body of regeneratedmaterial.

Immediately prior, to the reduction phase of my process thenickeliferous agent is in the oxidized state, at a temperature betweenabout 750 and 800 F., and comprises a complex mixture of nickel oxideand a porous support material plus nickel sulfate, small amounts ofnickel sulfide and carbonaceous materials, and perhaps other impurities.It should be emphasized the invention is unique to nickeliferous contactagents of the type described which are employed in a desulfurizationprocess and further, to such contacts which are regenerated bycombustion. This is because the unusual nature of the contact causes itto behave in a unique manner as compared with normally analogousmetallic oxides.

The reduction reaction of this complex mixture with hydrogen or otherreducing gases is highly exothermic. Therefore, if the reduction iseffected with no temperature control, an excess'ive temperature risewill occur in the. agent which will. cause sintering of the nickel ordisintegration of, the porous support, or both, and at the end of thereduction treatment the temperature. will be so high as to requireCOOllllg of the agent before introducing sulfur-containing oil for theensuing desulfurization cycle.

To allow the final temperature of the bed to exceed the'maximumallowable limit of about 875 F. is disadvantageous not only because ofthe danger of damaging the nickeliferous agent and/or the support butbecause of the high coke and gas production and rapid deactivation ofthe contact agent at temperatures exceeding this limit during thesubsequent processing period or on-streamphase. To attempt to avoid thelatter diinculty by cooling the reduced nickel agent after themaximumtemperature has been exceeded is entirely unsatisfactory, since thisinvolves depressuring, flushing with, for example, steam andrepressuring with. hydrogen. Under this procedure the length of theoff-stream period (non-productive time) is increased substantially,substantial quantities of hydrogen are wasted, a more complex control isnecessary, and the risk of deactivating the agent and/or support withthe cooling gas is created.

In view of the factsv discussed above, it will be obvious that anesesntial feature of my invention is the control of the initialtemperature at which the reduction is started and control of thetemperature during reduction utilizing certain amounts of steam mixedwith hydrogen to produce a reduction final temperature of thenickeliferous agentbetween abouti820 and 875 This temperature range issuitable for the de sulfurization phase of the process, and thus thecontacting of the sulfur-containing hydrocarbon vapors with theregenerated and reactivated nickeliferous agent may be resumed while theagent is still at approximately its final reduction temperature.

As an illustration of my invention, the following example shows atypical operating cycle with conditions for the on-strearn period, theregen- 1 eration period and the reduction period.

EXAMPLE The catalyst used was prepared by impregnation of dried 6-10mesh silica gel with an aqueous nickel nitrate solution followed bydrying at 250 F. and subsequent calcining at 800 F. to convert thenickel nitrate to nickel oxide.

This sequence. of. impregnation, drying and calcining was repeatedtwice, so that the final catalyst contained 18 per cent nickel oxide and82 per centv silica gel. ,The catalyst was then partially reduced bytreatingat 800 F. with hydro- Distillation, Percent at:

Liquid Recovery Vol. Percent; .Dry Gas, cu. ft./B

genand steam. The catalyst was then ready'for the reaction period. Aftera reaction period the reactor was depressured, and the catalyst wasregenerated by combustion. At the end of the regeneration period, inwhich the final temperaterminated and oil out into the reactor for aprocessing period. The conditions for the "-regeneration, reduction, andprocessing periods are given in the table below.

V Table 1 Regeneration step:

Pressure, p. s. i. g. Q. 1 100 Reactor Temperature, F.

' Outlet 1150 Steam rate, lbs/lb. oxidized catalyst 13 Air rate, SCF/lb.oxidized catalyst 29 Time, min. 120 Reduction step: v

Pressure, p. s. i. g 500 Reactor temperature, F.-'

Average 825 Maximum 850 Steam rate, lbs/lb. oxidized catalyst"; 1.50 Hzrate, SCF/lb. oxidized catalyst' 1.20 Steam-hydrogen mol ratio 26.421Reduction time, min. 15'

Operating step: Y I

Temperature, F 850 Pressure, p. s. i. g. 1 500 Space velocity, vol./vol1 Throughout, vol/vol. Cat 4 H2 circulation, CF/bbl 2000 Product dataare shown in Table 2 immediately below:

' Table 2 Charge and .Production Inspection:

Charge (Kuwait Crude) Product Carbon Midi 5'66 Carbon. Wt. Percent ofCharge.

The data -presented in Table 1 illustrate an operative example of thedesulfurization process utilizing the feature of controlled'reduction'of a supported nickeliferous' agent containing -25, per cent nickelcalculated as oxide. The data of Table 2 illustrate the benefitsobtained by this process, i. e., high degree of upgrading, high de notoccur, while above the maximum of about 7 875 Ethe rate ofdesulfurization doesnotma terially improve and a larger, more rapiddecomreducing gas with steam.

. 6 position of the oil to carbon and gas is encountered. Thus inreducing the nickeliferous agent by my process I raise the temperatureof the agent from its initial temperature of between about 750 and'800F. to at least about 820 F..

and I avoid a final reduction temperature of the agent higher than about875 F., by diluting the The amount of steam required varies with thetemperature rise to be obtained and .the initial temperature, arelatively large amount of steam being required to limit the temperaturerise to a small value. and a relatively smaller amount of steam beingrequired for a greater rise in temperature. The largest possibletemperature rise'that would be permittd. in my process is from 750 F. to875 F. or a'rise of F. vI have discovered that this particulartemperature rise of 125 F. can be obtained by employingin the reductiona steam-hydrogen ratio of 4.5 mols of steam per mol of hydrogen. Tolimit the temperature rise to less than 125 F. a larger amount ofsteamiin the steam hydrogen mixture isrequired. For example, I havefound that a ratio of 28 mols of steam per'mol of hydrogen is re quiredto limit the temperature to a 40 F. rise. To limit the temperature riseto any smaller value than 40 F. requires much larger and uneconomicalamounts of steam. For example 166 mols of steam per mol of hydrogenis-required to limit the temperature rise to 20 F.

Since such large amounts of steam are re-; quired ,to limit thetemperature rise to less than 40 F., it is undesirable to operate at atemperature differential of less than 40 F. both from'the 'standpoint ofsteam economy and the possibility of poor hydrogen efficiencyif thereduction gas is too dilute. f Thus, my invention involves the use of asteam-hydrogenratio which will produce a temperature rise intermediatebetween 40. and

125 F. is required, a steam-hydrogen mol ratio proportionatelyintermediate between 28:1 and 4.521 is employed.

Since 'it'is desirable to maintain a uniform catalyst bed temperatureduring the reduction step, the'reduction gases may be preheated so thatthe inlet temperature of these gases approaches' the desired initialtemperature for th reaction step. e

Thus, after regenerating the nickeliferous agent by oxidation underconditions which give a temperature or 750 to 800 F. for the oxidizedagent, Iselect'the proper steam-hydrogen ratio -.which will raise-theagent temperature during reduction at least 40 F. .from a point betweenabout750 and 800 F. to a desired point between about "820 and 875 F."The agent is then conwithout the necessity of first heating or coolinghydrogenfrom the desulfurization process gases absorbed in thedesulfurized product and removed therefromduring subsequentfractionation may be used. Also low molecular weight hydrocarbons suchas methane and ethane alone 'or-inadmixture with other hydrocarbons or.hy-

drogen may be employed.

\Vhat I claim is:

lpThe process for sulfurizing a hydrocarbon which comprises contactingvapors of a sulfurcontaining'hydrocarbon at elevated pressure and at atemperature between about 820 and 875 F.-with hydrogen and a'nickeliferous agent comprising between about and per cent nickelcalculated as oxide deposited upon a porous support, .a substantialportion of said nickel being in the .metallic form, terminating contactbetween the vapors, hydrogen, and .nickeliferous agent when regenerationis required, depressurizing, regenerating the nickeliferous agent bycombustion, at least partially reducing the regenerated nickeliferousagent by'treating said agent at an initial reduction temperature betweenabout 750 and 808 F. and at a pressure approximately equal to thereactionpressure with steam and simultaneously treating said agent witha reducing gas, the mol ratio of steam to reducing gas being betweenabout :1 and 28:1 and being such as to give said agent a finaltemperature after reduction at least about 48 F. higher than the initialreduction temperature but between about 820 and 375 F., terminating theflow of steam and immediately contacting vapors of the sulfur-containinghydrocarbon with hydrogen and the regenerated and at least partiallyreduced nickeliferous agent while still at approximately said finaltemperature and reaction pressure. i. g

2. The process'for desulfurizing a hydrocarbon which comprisescontacting vapors of asulfurcontaininghydrocarbon at elevated pressureand at a temperature between about 1820" and875 F. with hydrogen and anickeliferous contact agent comprising between about 15 and 25 per centnickel calculated as oxide deposited upon a porous support, asubstantial portion of, said nickel being in the metallic form,terminating contact between the vapors, hydrogen, and nickeliferouscontact agent when regeneration is required-depressuring, regeneratingthe nickeliferous con- 1 tact'agent by combustion .in the presence of,an oxygen-containing gas, controlling. the regeneration to give saidagent a temperature after regeneration ofbetween about 750 and 800-F.,

at least partially reducing therregeneratednick- I eliferous contactagent by treating said agent at approximately reaction pressure andwhile at about this temperature with steam and simultaneously treatingsaid agent with hydrogen, the molratio of steam to hydrogen beingbetween about 4.5:1 and 28:1 and being such as to give said agent afinal temperature after reduction at least about 40 F. higher than thetemperature at the beginning of the reduction treatment but betweenabout 820 and 875 F., terminating the flow of steam andimmediatelycontacting vapors, of the sulfur-containing hydrocarbon withhydrogen and the regenerated and at least partially reducednickeliferous contact agent while still at approximately said finaltemperature and reaction pressure.

3. The process for desulfurizing heavy hydrocarbons which comprisescontacting vapors of a sulfur-containing heavy petroleum oil at elevated8 pressure and at a temperature between about 820 and 875 F. withhydrogen and a nickeliferous contact agent comprising between about 15and 25 per cent nickel calculated as oxide deposited upon a poroussupport, a substantial portion of said nickel being in the metallicform, terminating contact between the vapors, hydrogen, andnickeliferous contact agent when regeneration is required, depressuring,regener ating the nickeliferous contact agent by combustion in thpresence of an oxygen-containing gas, controlling the regenerationtogive said agent a temperature after regeneration of between about 750and 800-F., at least partially reducing the regenerated nickeliferouscontact agent by treating said agent at approximately reaction pressureand while at about this temperature with steam and simultaneouslytreating said agent with hydrogen, the mol ratio of steam to hydrogenbeing between about 4.5:1 and 28:1 and being such as to give said agenta final temperature after reduction at least about 40 F. higher than thetemperature at the beginning of the reduction treatment but betweenabout 820 and 875 F., terminating the flow of steam and immediatelycontacting vapors of the sulfur-containing heavy petroleum oil withhydrogen and the regenerated and at least partially reducednickeliferous contact agent while still at approximately said finaltemperature and reaction pressure.

4. The process for desulfurizing a hydrocarbon oil which comprisescontacting vapors of a sulfur-containing hydrocarbon oil from the groupconsisting of total crude, topped crude, and reduced crude at elevatedpressure and at a temperature between about 820- and 875 F. withhydrogen and a nickeliferous contact agent comprising between about 15and 25 per cent nickel calculated as oxide deposited upon a poroussupport, a substantial portion of said nickel being in the metallicform, terminating contact between the vapors, hydrogen, andnickeliferous contact agent when regeneration is required, depressuring,regenerating the nickeliferous contact agent by combustion in thepresence of an oxygencontaining gas, controlling the regeneration togive said agent a temperature after regeneration of between about 750and 800 at least partially reducing the regenerated nickeliferouscontact agent by treating said agent at approximately reaction pressureand while at about this temperature with steam and simultaneouslytreating said agent with hydrocarbon, the mol ratio of steam to hydrogenbeing between about 4.5:1 and 28:1 and being such as to give said agenta final temperature after reduction at least about 40 F. higher than thetemperature at the beginning of the reduction treatment but betweenabout82fl" and 875 F.,terminating the flower" steam and'irnmediatelycontacting vapors of. the sulfur-containing hydrocarbon oil withhydrogen and the regenerated and at least partially reducednickeliferous contact agent while still at approximatelysaid finaltemperature and reaction pressure.

" VINCENT L. CRAWFORD.

References Cited in the file of this patent 2,560,433 Gilbert et a1 July1-0, 1951

1. THE PROCESS FOR SULFURIZING A HYDROCARBON WHICH COMPRISES CONTACTINGVAPORS OF A SULFURCONTAINING HYDROCARBON AT ELEVATED PRESSURE AND AT ATEMPERATURE BETWEEN ABOUT 820* AND 875* F. WITH HYDROGEN AND ANICKELIFEROUS AGENT COMPRISING BETWEEN ABOUT 15 AND 25 PER CENT NICKELCALCULATED AS OXIDE DEPOSITED UPON A POROUS SUPPORT, A SUBSTANTIALPORTION OF SAID NICKEL BEING IN THE METALLIC FORM, TERMINATING CONTACTBETWEEN THE VAPORS, HYDROGEN, AND NICKELIFEROUS AGENT WHEN REGENERATIONIS REQUIRED, DEPRESSURIZING; REGENERATING THE NICKELIFEROUS AGENT BYCOMBUSTION, AT LEAST PARTIALLY REDUCING THE REGENERATED NICKELIFEROUSAGENT BY TREATING SAID AGENT AT AN INITIAL REDUCTION TEMPERATURE BETWEENABOUT 750* AND 800* F. AND AT A PRESSURE APPROXIMATELY EQUAL TO THEREACTION PRESSURE WITH STEAM AND SIMULTANEOUSLY TREATING SAID AGENT WITHA REDUCING GAS, THE MOL RATIO OF STEAM TO REDUCING GAS BEING BETWEENABOUT 4.5:1 AND 28:1 AND BEING SUCH AS TO GIVE SAID AGENT A FINALTEMPERATURE AFTER REDUCTION AT LEAST ABOUT 40* F. HIGHER THAN THEINITIAL REDUCTION TEMPERATURE BUT BETWEEN ABOUT 820* AND 875* F.,TERMINATING THE FLOW OF STEAM AND IMMEDIATELY CONTACTING VAPORS OF THESULFUR-CONTAINING HYDROCARBON WITH HYDROGEN AND THE REGENERATED AND ATLEAST PARTIALLY REDUCED NICKELFEROUS AGENT WHILE STILL AT APPROXIMATELYSAID FINAL TEMPERATURE AND REACTION PRESSURE.